Efficacy and safety of nanohybrids comprising silver nanoparticles and silicate clay for controlling Salmonella infection

Developing effective and safe drugs is imperative for replacing antibiotics and controlling multidrug-resistant microbes. Nanoscale silicate platelet (NSP) and its nanohybrid, silver nanoparticle/NSP (AgNP/NSP), have been developed, and the nanohybrids show a strong and general antibacterial activity in vitro. Here, their efficacy for protecting Salmonella-infected chicks from fatality and septicemia was evaluated. Both orally administrated NSP and AgNP/NSP, but not AgNPs alone, effectively reduced the systemic Salmonella infection and mortality. In addition, quantitative Ag analyses demonstrated that Ag deposition from AgNP/NSP in the intestines was less than that from conventional AgNPs, indicating that the presence of NSP for immobilizing AgNPs reduced Ag accumulation in tissue and improved the safety of AgNPs. These in vivo results illustrated that both NSP and AgNP/NSP nanohybrid represent potential agents for controlling enteric bacterial infections

Novel Nanohybrids of Silver Particles on Clay Platelets for Inhibiting Silver-Resistant Bacteria

We develop a novel nanohybrid showing a strong antibacterial activity on all of the tested pathogens, including methicillin-resistant Staphylococcus auerus and silver-resistant E. coli. The nanohybrid consists of silver nanoparticles (AgNPs) supported on 1 nm-thick silicate platelets (NSPs). The AgNP/NSP nanohybrid enables to encapsulate bacteria and triggers death signals from the cell membrane. The geographic shape of the NSPs concentrates AgNPs but impedes their penetration into attached cells, mitigating the detrimental effect of silver ion deposition in applied tissues. Moreover, the tightly tethered AgNPs on NSP surface achieve a stronger biocidal effect than silver nitrate, but bypassing Ag+ mechanism, on silver-resistant bacteria. This nanohybrid presents an effective and safe antimicrobial agent in a new perspective

Controlling salmonella infection in chicken by nanohybrids of silver and clay

已知奈米銀粒子，對各種病原體具有殺菌能力。為分散奈米銀粒子與防止奈米銀進入細胞對動物體產生毒性，本篇研究材料使用完全脫層後的蒙脫土（NSP）作為奈米銀粒子的分散劑，形成奈米銀╱奈米脫層黏土（AgNP/NSP）的複合材料。先期的體外（in vitro）研究已經證實AgNP/NSP可以有效的抑制多種病原體的生長，其中也包含了沙門氏桿菌。本論文的目的在於進行AgNP/NSP的體內（in vivo）研究，測試其安全性與控制沙門氏桿菌感染雛雞的有效性。雛白痢沙門氏桿菌會使幼雞呈現急性全身性感染造成高死亡率，是一種很嚴重的敗血性傳染疾病。實驗中對出生一日齡的雛雞餵食雛白痢沙門氏桿菌六次（5×109CFU/次），每次間隔12小時，並且在第二次餵食細菌後六小時口頭給予0.2 wt％ AgNP/NSP。實驗發現可以有效地降低雛雞因感染雛白痢沙門氏桿菌所造成的死亡率。此外，鼠傷寒沙門氏桿菌亦常引起家禽細菌性腸炎。實驗也發現給予雛雞0.2 wt％ AgNP/NSP，可以減少此菌經感染雛雞腸胃道後，再移行感染其他臟器的頻率。除此之外，將AgNP/NSP和抗生素Amoxicillin合併使用，有提升其治療細菌感染的效果。在安全性測試上，我們證實在連續投與1.0 wt% AgNP/NSP十天後，對雛雞的生長與體內腸道不會造成影響。以上結果顯示，AgNP/NSP可以提供控制家畜禽消化道細菌感染的一種新穎且安全有效的治療藥劑。Silver nanoparticle (AgNP) is a well-characterized antibacterial agent. Our previous studies have shown that the Nanosilicate platelet (NSP) is an ideal dispersant for the fabrication of AgNP to ameliorate the drawback of the self-aggregation of AgNP and silver deposite in applied tissues. AgNP/NSP has shown that effective inhibition of the growth of various pathogens in vitro, including the enteric Gram-nagetive Salmonella. The aim of this study is to evaluate the in vivo antibacterial effect of AgNP/NSP on Salmonella infection in chicks. Salmonella pullorum (S. pullorum) is a highly contagious pathogen, which often causes a high mortality in the infected chicks. In this thesis, we continuously fed new-hatched chicks with S. pullorum by oral administration for six times at 12 hr interval and 0.2 wt% AgNP/NSP was applied once after 6 hr following the secondary administration. The results showed that AgNP/NSP effectively reduced the mortality of chick caused by S. pullorum. In addition, S. typhimurium is another important enteric-pathogen in poultry. We showed that 0.2 wt% AgNP/NSP significantly mitigated the transmission of S. typhimurium from infected gastrointestinal (GI) tract to other internal organs. Notably, AgNP/NSP potentiates the antibacterial effect of amoxicillin on the control of Salmonella infection. Especially, continuous administrations of 1.0 wt% AgNP/NSP for 10 days to chicks did not cause undesired cytopathic effect and silver deposits in the GI tracts. Taken together, these results suggest that AgNP/NSP is a potential therapeutic reagent to control the bacterial infection in GI tract for domestic animals.目次 中文摘要....................................................i 英文摘要...................................................ii 目次 ....................................................iii 圖表目次...................................................iv 前言.......................................................1 材料與方法..................................................6 結果......................................................12 討論......................................................18 參考文獻...................................................23 結果圖表…..................................................27 附表......................................................42 附圖......................................................44 圖表目次 圖一、AgNP/NSP結構說明圖.....................................27 圖二、餵食細菌的時間示意圖....................................28 圖三、AgNP/NSP治療雛雞之存活率觀察............................29 圖四、對照組雛雞之病理切片染色.................................31 圖五、感染雛白痢沙門氏桿菌雛雞之病理切片染色......................32 圖六、雛雞菌血症觀察.........................................33 圖七、雛雞臟器感染之判讀......................................34 圖八、抗生素與AgNP/NSP合併使用治療雛雞之存活率觀察...............35 圖九、餵食高濃度AgNP/NSP和NSP之雛雞代謝觀察....................36 圖十、餵食高濃度AgNP/NSP和NSP對雛雞存活率之觀察.................37 圖十一、餵食高濃度AgNP/NSP和NSP之雛雞體重分析...................38 圖十二、餵食高濃度NSP之雛雞病理切片.............................39 圖十三、餵食高濃度AgNP/NSP之雛雞病理切片........................40 圖十四、感應耦合電漿質譜（ICP-MS）分析..........................41 表一、病理評估標準...........................................42 表二、個別雛雞之組織病理變化...................................43 附圖一、場發式電子顯微鏡觀察沙門氏桿菌與AgNP/NSP的交互作用.........4